Stabilization of organic substances



Patented Mar. 5, 1946 s PATENT GFFICE STABILIZATIQN or ORGANIC SUBSTANCES Richard G. Clarkson, Wilmington, Del., assigncr to E. I. du Pont de Nemours & Company, Wilmington, Del., a corporation of Delaware UNITED srAT-s No' Drawing. Application August 12, 1942, Serial No. 454,613

13 Claims.

bilization of such substances which are subject I to deterioration caused by the action of molecular oxygen and catalyzed by'metals and their compounds.

Many organic products, such asfats, drying oil, rubber, petroleum products, photographic developers and synthetic unsaturated compounds, are readily attacked by oxygen and the resulting deterioration imparts undesirable qualities. to them and eventually destroys their usefulness.

Signal success has been achieved in recent years, in the preservation of many organic substances, by the discovery and use of compounds generically called oxidation inhibitors or antioxidants. These agents, mostly oxidizable organic compounds, retard the auto-catalytic process. Since antioxidants are themselves oxidized in the course of time, as a result of auto-oxidation, the beneficial effect obtained by their use is not permanent, and theyprotect the organic substances only so long as they are not rendered inactive. They are, moreover, very specific in action, each group of auto-oxidizable substances requiring a different type of antioxidant for the best results. H

Vanadium, chromium, manganese, iron, cobalt, copper and theircatalyticall active compounds accelerate the rateof oxidation of many organic substances. For example, it is'well known that copper compoundssp'eed the formation of gum in cracked gasoline and the aging 'ofrubber; that-cobalt compounds promote the oxidation of drying oilsgand that ironcompounds catalyze the deterioration of lubricatingoils. They also accelerate the oxidation of aromatic hydroxy and amino antioxidants used to stabilize thesev oxidizable substances. Hence, these metal catalysts and the antioxidants are antagonistic in action, and the normal inhibiting effect of the latter is greatly reduced in the presence of the former. r

Metal compounds occur naturally in many organic products, but often in such slight traces as to cause very little harm. Their concentrations, however, are frequently raised during the course of handling and utilizing the products; vessels and conduits made of metals containing copper or iron are used for storage and transportation, or ingredients contaminated with metal compounds might be added.

The harm done by these extraneous catalysts may be prevented by at least three methods: 1) their removal by purification, but often this is practically impossible of accomplishment and usually too costly to be economically feasible, (2) the addition of. a sufficient amount of an antioxidant so that its preserving effect is. equal or greater than the pro-oxidant effects of the metal catalysts present, but the efiectiveness of the antioxidant is so greatly diminished by the metal catalysts that the advantage gained under this circumstance is seldom worth the cost of the increased quantity of antioxidant required for adequate stabilization, and (3) the suppression of the catalytic activity of the metal compounds by chemical means without physically removing them from the system.

It is an object of the present invention to retard the. deterioration of organic substances causedby' the action of molecular oxygen and promoted by the presence of certain metal catalysts and their catalytically active compounds. Another object is to render antioxidants, which are relativel ineffective in the presence of metal catalysts and their catalytically active compounds, efiective to inhibit the oxidation of oxidizable organic substances even in the presence of metal catalysts and their catalytically active compounds. A further object-is to provide a newplass of metal deactivatorswhich are effective to render metal catalysts inactive to catalyze the oxidation of oxidizable organic sub stances containing or in contact with such metal catalysts. A more particular object is to inhibit the deterioration of petroleum hydrocarbons in the presence of metal catalysts and their catalytically active compounds. Other objects are to provide new compositions of matter and-to advance the art. Still other objects willappear hereinafter.

The above and other objects may be acc0mplished in accordance with my invention which comprises adding to organic substances, normally subject to deterioration caused by the action of molecular oxygen, and containing a catalyst of the group of vanadium, chromium, manganese, iron, cobalt, copper and their compounds, normall eirective to catalyze oxidation of said organic substances, 2. metal deactivator in a small proportion suflicient to deactivatesuch catalyst, such metal deactivator having the formula 1 wherein R and R represent hydrogen atoms or organic radicals. The organic substance also may and generally will contain anantioxidant which is normally e-Ifective to retard oxidation of the organic substance in the absence of the metal catalyst. I have found that such metal deactivators are capable of efiectively suppressing the catalytic activity of vanadium, chromium, manganese, iron, cob-alt, copper and their catalytically active compounds and hence will render such catalysts-iinefiective to catalyze .:the oxidation of the organic substance, including any-antloxidant which may be present.

The organic substances, which may be treated in accordance with my invent-ion,.inc1ude animal and vegetable fats and oils, edible oils, fruit and vegetable juices, textile fibres, photographic fdevelopers, antioxidants, synthetic unsaturate'd compounds, petroleum hydrocarbons, rubber-and the like. My metal deactivators:are'particularly desirable in liquid petroleum hydrocarbonss-an'd especially in gum-forming hydrocarbon distillates, such as, for example, cracked gasoline. ierally, ;in :practice, the organic -:substance, tparticularly the petroleum hydrocarbons, will :also .contain an antioxidanttwhich isznormally reflec- ;tive 'tov materially retardthedeterioration :oreoxi- :dation ofrthe organicsubstance.infthe absence of :the icatalytically active metals, ;but .which :is .less effective-in :thepresenceof suchlmetals.

'Themetal deactivators of my inventionmust ,containgasianucleus,.theJgroup NH-$!i-NH'NH It appears that this groupingis the acti-ve grouping which provides "the metal deactivatingmrop- .erties for the compounds. groups,--satisfyingtherfree valences, maybe widely varied-anddo not appear toaffect the functions .of the'groupingin deactivating the metalcatal-ysts, but merely afiect the solubility of" the compounds in the organic substances. and preferred member I of the "class I is: thiosemi- .c-arbazide wherein R and R in theformula R- NH- fi)- NHNH-B represent hydrogenatoms. In the-other-compounds within the class of metaldeactivators-bf .my'invention, either one or both of Brand. R, may represent organic groups such as. aliphatic radicals, aromatic ,radicals, heterocyclic. radicals wherein R represents an organic radical. R andR, .in-the formula R-e-NH-fi-NH-e-NJIR' When Gen-

The 2 elements and The simplest represent organic radicals other than -("JNH-R such radicals are preferably hydrocarbon radicals, such as alkyl, cycloalkyl, alkaryl, aralkyl and aryl radicals.

efinitecoperative concentrations'of the metal *deactivater" in the organic substance cannot be specified for each case as the quantity required is -.dependent upon the amount of metal catalyst presentintheorganic substance. The metal deactivator shouldbe present in the proportion of approximatlyt'rto'lt) times the amount of the rmetal'catalyst present, on the basis of the metallic zelementgin-order to obtain complete deactivartion of .themetal catalyst. Higher proportions o'f metal deactivator may be employed, particularly when a reservoir of metal is present in the form of metal in bulk in contact with the organic substance. :Generally, from about 0.0001:% to about..0.1,%,,based .onthe weight of the organic substance, will-he sufiicientior most purposes, particularly when the organic substance is ,a; liquid; petroleum:hydrocarbomsuch a a gum-forming hydrocarbon distillate of the character of cracked-gasoline.

The-.catalytically active metal and its compounds maybe dissolved in the organic substance .or suspendedtherein or may '.be-in the form of metal= in bulk in intimate contact with the organic substance. v-It wi1l lee-understood that, when I refer-.toan; organic substance containing a catalyst, I mean toiinclude those-cases wherein the metal-in bulkfformis in-contact with the organic substance, as -well,=as those cases wherein the .catal-ytically active metal is dissolved or suspended in the organic substance.

.For the bestresults, the deactivator should; be solubleiinrthe organic substance to' be protected. Solubility in organic substances is increased by the presence. ctr-hydrocarbon radicals on the nitrogen atoms in the positionsrepresented: by Brand Rfiin theformula The deactivators maybe addedtothe oxidizable organic substances to-be protected in any form and .manner. They may be in solid-or liquid form,, mixed 'with' otherzadditional agents or dissolved .in a solvent. They may be dissolved in the organic substance or dispersed therein in-any suitableimanner. .They maybe added to the fin- .ishedorganic substance or to the organic :substanceat-any stage in. its manufacture.

.In .order :to :avoid confusion arising from :a superabundance of data, cracked :gasoline has beenrselectedjasan example; of an auto-oxidizable organicsubstance-for. the purposes of illustration. .The 45311113165 of --gasoline used in'the following tests .were-either'cracked gasolines or blends of cracked and straight-run gasolines, completely refined, but :otherwise untreated with chemical agents, .suchfas dyes, anti+knocks and antioxidants. sinceggasoline is atmixture'of variable composition, identical results are not obtained with/difierent samples. The magnitude ofthe effectsris great enough, however, .to render :this difference-relatively insignificant.

gpeBenzylamin-ophenol, ;ab:breviated BAP, has been chosen as ea representative gasoline :antioxidant. 'ilhez'metals present as catalysts were employed 5STthEiI'J.O-16&t-ES. .The concentrations of the antioxidants-and-the metal deactivators are U088 HBTBFGHCB Search Boom givenin weight percent in gasoline. The concen trations of the metals are given in parts per million by weight of the metal rather than by weight of the metal oleate.

The term stabilized gasoline is employed to mon catalyst occurring in gasoline, other metals also accelerate the oxidation of gasoline. The catalytic effects of manganese, cobalt and iron, and their suppression by thiosemicarbazide are shown in Tables IV, V and VI.

denote gasoline to which has been added an Table IV anti-oxidant in sufiicient quantity to significantly increase its induction period in the absence of Cone added metal catalysts Cone. thio- N0. Catalyst Gone. Ind. per. The accelerated method, used for determining 10 BAP ig g' the induction periods given below, was the one described in J. I. E. C. 25, 397 (1933). It consists in heating 100 cc. of gasoline at 100 C. in lvlinutes a 1 liter pyrex flask containing pure oxygen. The internal pressure is observed every 10 minutes 570 by means of a manometer attached to the system. The elapsed time from the start of the 300 test until the gasoline begins to adsorb oxygen at the rate of cc. per 10 minutes or higher, Table V as shown by the fall in internal pressure, is taken as the induction period. It has been found Com that the induction period, obtained by this me- NO cncone. io- Ind Per BAP C0. semicarthod, although greatly shortened, 1s a fairly ac- 1mm curate measure of the relative stability of gasoline under normal storage conditions. 2 Weight might at M'vt! Table I e, e, 0.0 200 0.0 100 No C83? Deaotivator Conc. 001 290 Weight Weight Table VI percent P.P.M. percent Minutes 1.... 0.0 0.0 120 2 0. 001 0.0 310 Induction periodin 3 0.001 1.0 55 minutes 4 0.001 1.0 300 5 0.001 1.0 Dithiourea 340 No I Absence of Preset-Ice of thiosemi- It will be observed that the harmful effect of carbazide giifgg copper is completely counteracted by thiosemicarbazlde and dlthlourea 4.0 1 Gasoline+0.00l% BAP+2 P. P. M.

Table [I Fe 320 380 Induction period in The effect of thiose micarbazide on the copper minutes dish gum test is shown in Table VII.

Absence of Presence of Table VII 0.01 percent l-phenyl hen g g g th loser i- N0 Conc. gg s Copper r carbazide BAP carbaiide dish gum Gasoline 0.007% p-(n-butylamino)- Weight Weight 45 230 percent percent JvIg./100 cc.

. 1 0. 0.0 14.0 0.001 0.0 50 It W111 be noted that 1-phenylth1osem1carbaz1de 0. 0 0. 00s as counteracts the effect of copper. r M01 M05 22 In certain samples of gasoline, even in the absence of added metal catalysts, thiosemicarbazide increases the induction period of gasoline and enhances the eificiency of the antioxidant present as shown by Table III. This is probably due Thiosemicarbazide has also been found useful in counteracting the harmful effects of copper in synthetic rubber latex, in the manufacture and application of organic dyes, and in other copper contaminated systems. to catalytlc metals already present While the above tests show the results with Table III only copper, manganese, iron and cobalt, similar results were obtained with vanadium and chro- "nducmium. Cmpmmd 00m d It will be understood that the experiments and tests, hereinbefore given, have been given for Weight illustrative purposes only. Many variations and percent Minutes modifications can be made in my invention withgg'it out departing from the spirit or scope thereof. BIZ. 0.002 400 Themetal deactivators of my invention can be 3:; f% fff f} if f- 8: employed in other organic substances, the metals a... BADPM: 0.001 380 may be present in other forms and other com Thwsemmarbazlde M01 pounds, within the broad scope of my invention, v may be substituted for the compounds specifically Although copper is the most potent and comreferred to hereinbefore. While I have disclosed theuse of single metal deactivators, it will be apparent that mixtures oi two or more metal deactivators otmy invention may be employed it desired;

Besides many others, the following compounds are metal deactivators Within the scope of my invention.

'I'hiosemicarbazide l-ethyldithiourea 1,6-dimethyldithiourea 1- (n-butyl) dithiourea 1 alpha-pyridyl) dithiourea It will be apparent that, by my invention, I am able to effect the stabilization of organic substances susceptible to the harmful action of molecular oxygen catalyzed by vanadium, chromium, manganese, iron, cobalt, copper and their catalytically active compounds. This stabilization may be accomplished, in accordance with my invention, by the addition of metal deactivators either alone or in combination With an amount of an antioxidant sufficient to stabilize the substance in the absence of metal catalysts. It is often technically and economically unfeasible to counteract the catalytic effects of such metals by means of an antioxidant alone. I believe that. the metal deactivators of my invention function. by forming very stable complexes with the metals, which complexes are catalytically inactive. It appears that the metal deactivators of my invention, in general, are not antioxidants. However, my invention is not to be limited by any theory as to the manner in Which the metal deactivators function to produce. the results.

I claim:

I. Aeomposition comprising an organic substance, normally subject to deterioration caused by the action of molecular oxygen, containing a catalyst of the group consisting of vanadium, chromium, manganese, iron, cobalt, copper and their compounds, normally efiective to catalyze oxidation of said organic substance, a small proportion of p-benzylaminophenol, normally effective to materially retard such deterioration in the absence of said catalyst but which is less efiective in the presence of said catalyst, and

wherein R and R represent members selected from the group of hydrogen and organicradicals.

2. A composition comprising an organic substance, normally subject to deterioration caused,

by the action of molecular oxygen, containing a catalyst of the group consisting of vanadium, chromium, manganese, iron, cobalt, copper and their compounds, normally effective to catalyze oxidation of said organic substance, a small proportion of p-benzylaminophenol', normally-effective tomaterially retard such deterioration in the absence of said catalyst but which is less effective in the presence of said catalyst, and having incorporated therein a metal deactivator in a. small .proportion sufficient to deactivate said catalyst, said metal deactivator being thiosemicarbazide,

3. A composition. comprising an organic substance, normally subject to deterioration caused by the action of molecular oxygen, containing a catalyst of the group consisting of vanadium, chromium, manganese, iron, cobalt, copper and their compounds, normally efiective to catalyze oxidation of said organic substance, a small proportion of p-benzylaminophenol, normally effective to materially retard such deterioration in the absence of said catalyst but which is less effective in the presence of said catalyst, and having incorporated therein a metal deactivator in a small proportion sufficient to deactivate said catalyst, said metal deactivator having the formula ing incorporated therein a. metal deactivator in. a small proportion sufiicient to deactivate said catalyst, said. metal deactivator being dithiourea. 5. A composition comprising cracked gasoline, normally subject to deterioration caused by the action of molecular oxygen, containing a catalyst,

of-the group consisting o-i'l vanadium, chromium, manganese, iron, cobalt, copper and their compounds, normally eiiective to catalyze oxidation of said cracked gasoline, a small proportion of a p-benzylaminophenol, normally effective to materialll retard such deterioration in the absence of said catalyst but which is less efiective in the presence of said catalyst, and having incorporated therein a metal deactivator in a small proportion suificient to deactivate said catalyst, said metal deactivator having the formula R-NH-flJ-NH-NH-B wherein R; and R represent members selected from the group of hydrogen and organic radicals.

52 UUF'EPUSE l EUNS.

Cross Reference 6. A composition comprising cracked gasoline, normally subject to deterioration caused by the action of molecular oxygen, containing a catalyst of the group consisting of vanadium, chromium, manganese, iron, cobalt, copper and their compounds, normally effective to catalyze oxidation of said cracked gasoline, a small proportion of p-benzylaminophenol, normally efiective to materially retard such deterioration in the absence of said catalyst but which is less eifective in the presence of said catalyst, and having incorporated therein a metal deactivator in a small proportion sufficient to deactivate said catalyst, said metal deactivator being thiosemicarbazide.

7. The method of inhibiting the catalytic oxidation of an organic substance caused by a catalyst of the group consisting of vanadium, chrmium, manganese, iron, cobalt, copper and their compounds which comprises incorporating in said organic substance a small proportion of p-benzylaminophenol, normally effective to materially retard such deterioration in the absence of said catalyst but which is less efiective in the presence of said catalyst, and a small proportion, sufflcient to deactivate said catalyst, of a metal deactivator having the formula cracked gasoline a small proportion of p-benzylaminophenol, normally efiective to materially retard such deterioration in the absence of said catalyst but which is less efiective in the presence of said catalyst, and a small proportion,

sufiicient to deactivate said catalyst, of a metal 1 deactivator having the formula R-NH-(fi-NH-NH-Jt' wherein R and R represent members selected from the group of hydrogen and organic radicals.

9. A composition comprising an organic substance, normally subject to deterioration caused by the action of molecular oxygen, containing a catalyst of the group consisting of vanadium, chromium, manganese, iron, cobalt, copper and their compounds, normally effective to catalyze oxidation of said organic substance, a small proportion of p-benzylaminophenol, normally effective to materially retard such deterioration in the absence of said catalyst but which is less effective in the presence of said catalyst, and having incorporated therein a metal deactivator in a small proportion sufficient to deactivate said catalyst, said metal deactivator having the formula wherein R" is selected from hydrogen and hydrocarbon radicals and X is selected from O, S and NHR.

10. A composition comprising an organic substance, normally subject to deterioration caused by the action of molecular oxygen, containing a catalyst of the group consisting of vanadium, chromium, manganese, iron, cobalt, copper, and their compounds, normally effective to catalyze oxidation of said organic substance, a small proportion of p-benzylaminophenol, normally effective to materially retard such deterioration in the absence of said catalyst but which is less effective in the presence of said catalyst, and having incorporated therein a metal deactivator in a small proportion sufilcient to deactivate said catalyst, said metal deactivator having the formula RNH-("3NH-NHa wherein R represents an organic radical.

11. A composition comprising petroleum hydrocarbons, normally subject to deterioration caused by the action of molecular oxygen, containing a. catalyst of the group consisting of vanadium, chromium, manganese, iron, cobalt, copper and their compounds, normally elfective to catalyze oxidation of said petroleum hydrocarbons, a small proportion of p-benzylaminophenol, normally efiective to materially retard such deterioration in the absence of said catalyst but which is less efiective in the presence of said catalyst, and having incorporated therein a metal deactivator in a small proportion sufficient to deactivate said catalyst, said metal deactivator havng the formula wherein R and R represent members selected from the group of hydrogen and organic radicals.

12. A composition comprising cracked gasoline, normally subject to deterioration caused by the action of molecular oxygen, containing a catalyst of the group consisting of vanadium, chromium, manganese, iron, cobalt, copper and their compounds, normally effective to catalyze oxidation of said cracked gasoline, a small proportion of p-benzylaminophenol, normally efiective to materially retard such deterioration in the absence of said catalyst but which is less efiective in the presence of said catalyst, and having incorporated therein a metal deactivator in a small pro- 5 portion sufficient to deactivate said catalyst, said metal deactivator having the formula NHz-(fi-NH-NH-dt' wherein R"represents an organic radical.

13. A composition comprising cracked gasoline, normally subject to deterioration caused by the action of molecular oxygen, containing a catalyst of the group consisting of vanadium, chromium, manganese, iron, cobalt, copper and their compounds, normally eflective to catalyze oxidation of said cracked gasoline, a small proportion of p-benzylaminophenol, normally efiective to materially retard such deterioration in the absence of said catalyst but which is less effective in the presence of said catalyst, and having incorporated therein a metal deactivator in a small proportion sufiicient to deactivate said catalyst, said metal deactivator being dithiourea.

RICHARD G. CLARKSON.

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